Gas pouring out of intake bells

[D0wn5h1ft]

Ok, so as some of you already know I'm in phase 1 of a '79 standard rebuild. The bike didn't come with carbs so i picked up a set of MNS carbs for a nice chunk of changed. Cleaned and rebuilt them and I was getting bowl overflow issues even thought I had set the heights correctly.

Recently, I tore the carbs down again and put in new float bowl needles, new float needle assembly o-rings, new float bowl gaskets, and set the float height. I put it on the bike and I've stopped the overflow BUT now gas is just pouring out of the intake bells. It's not the normal aerosolized gas that comes out of them during normal operation but it's really coming out.

Here's the procedure I used for setting the float height levels. Took the float bowls out, flipped the carbs over, in the resting position set all the float heights to 23mm, and then reassembled.

Here's my thoughts: I think even though everyone says to set your float heights to 23mm I really need to set them higher (~26mm) because I'm blowing gas out of the intakes on ALL FOUR now not just #1 like before.

Any suggestions?

For a reference, I set the heights where I was told to in this thread: http://www.xs11.com/forum/showthread...t=float+height

Which is the highest part of the floats to the carb body gasket surface.

[D0wn5h1ft]

BIG QUESTION: I don't have to compress the floats down when I measure, do I? Because they have a little bounce to them due to the float needle spring.

[sparkfly88]

If they are plastic you want the 23mm measurement,

You dont want to compress em, that bounce you feel is a spring inside the needle.

You want to measure 23mm from the carb surface without the gasket on it.

The floats should look pretty level if they are done properly.

[jjz28]

I don't know if this applies to you but I had to trim my bowl gaskets because my floats were "dragging" on the gaskets. I don't know the years of carbs that have the different settings and plastic floats but my 79 has metal floats and I set them at 1" I believe it is.

[sparkfly88]

I trimmed all my gaskets as well, plastic floats hung up.

[D0wn5h1ft]

If they are plastic you want the 23mm measurement,

You dont want to compress em, that bounce you feel is a spring inside the needle.

You want to measure 23mm from the carb surface without the gasket on it.

The floats should look pretty level if they are done properly.

See mine aren't that level at 23mm. That flat surface on the floats still has an angle on it and I've checked it a bunch of times now. If it were level, I'd have an even bigger problem because the height of the gas in the bowl would be even higher. I'm thinking about just setting the height to 26mm because obviously something is causing me to measure a height that is quiet a bit lower than it should be.

I'm going to check to see if my floats are getting hung up though first. It did look like they were when I had the carbs upside down but who knows.

[natemoen]

See mine aren't that level at 23mm. That flat surface on the floats still has an angle on it and I've checked it a bunch of times now. If it were level, I'd have an even bigger problem because the height of the gas in the bowl would be even higher.

And there is your problem perhaps......

Moving the float level like that IS NOT THE ANSWER! When set the float height you are actually setting it 8 times. Each side of the float needs to be at the same level of 23mm from the gasket sealing surface with the gasket removes. You can twist and bend the connecting part of the float to level the pair's.

[rdmcguy]

A stupid question maybe

Not being as familiar as some, with the carbs you have.
How many fuel lines do you have going in?
I don't know if yours have the upper two that should go to the air box,
or vented elsewhere,but if you have fuel going into all four
That is your problem.
Good luck

[MPittma100]

Gas Leak

Ok, fuel is leaking into air box. So what is wrong? Is it the float level setting? Is it a float hanging open on a gasket and not closing? Is it trash in one or more of the needle and seats? Have you tried tapping on the carbs/bowls of the ones that are leaking?

Smart thing to do after making sure there is no trash in any of the needle valves and verifying float levels are correct is to attach the tank remotely to the carbs before putting them onto the engine. If they are leaking, it is a lot easier to fix them.

Verify the correct float height for the particular carburetor and float that you have.

They will not leak when they are correctly setup. That is what you have to look forward to. You will eventually get them to this point.

Mike

[motoman]

As MPittma suggested, with bowls off, flip that carb bank upside down with floats intact, setting fuel tank above carbs and watch for any leaking around seats. If no leaking, liklyhood of bowl gaskets touching side of float when bowl is tightened down is pretty good. Leaving gasket in place, use an X-acto knife and trim inside edge of gasket, even if it 'looks' like it won't touch float.
AS Nate stated, throwin' a different float setting in the mix is just going to compound other running issues, trust me, BTDT with every setting from 22mm-31mm. What I DID find, playing with fuel levels is one millimeter change of float is equivelant to 2-2.5mm of acual fuel levels. Not alot of volume area left in there for fuel once floats are in there.
FWIW, a half of millimeter of fuel height in there WILL drasticly change how bike runs. This is specificly why it is important to get ALL eight floats identically the same. If these are the later carbs, your idea of 26mm WILL run it too lean, and starve for fuel on the top-end.......and eventually WILL 'ventilate' a piston or two.

[DGXSER]

A few thoughts for you. First test is the upside down bench test. Set the float heights to 23 mm, then hook up a fuel source. Blip each float to get the air out, dry the bowl and such with towels and or compressed air. Now take a break, go eat lunch, come back and look for signs of leaking. If its dry move to test 2. If its wet, your needle valve, seats or both are dirty or worn. Or you tore the o rings when installing the seats.

Test 2, put the bowls on, turn carbs right side up, set them level front to back and side to side, add fuel. Watch for leaks. Sometimes you do need to tap the float bowl to get them to stop leaking. I always trim the gasket back so there is no overhang.

Only after passing both test do I mount them on the bike.

[Tat2demon]

Didnt happen to forget to put the fiber washers in between the body and the new seats did ya?

[D0wn5h1ft]

Didnt happen to forget to put the fiber washers in between the body and the new seats did ya?

Fiber washers? Where at specifically?

[bikerphil]

The later type carbs with the O-ring seats do not use the fiber washer, only the early type does.

[D0wn5h1ft]

Ok, so here it goes. I'm going to need some help with this one.

I did the "upside-down" bench test [I hooked up the carb bank to one of my petcocks and threw it to "prime" when the carbs were upside down with the float bowls off] and I am now covered in gasoline. There was gas coming out from around the float needles (not the seats where the brand new o-rings are at) like my momma didn't know. And this happened on all 4 carbs. It was slower-ish coming out on the #3 and #4 carb but still really pouring out. I even tried pressing down one of the floats manually and it didn't even slow the rate of flow. Also, I tried taking off one of the floats and pushing down on the float needle and no change in the leaking.

Like I mentioned before, I already replaced the float needle seat o-ring (and checked to make sure I didn't rip them) and I have already replaced my float needles. I'm not really sure what the next step is.